![]() It added breadth to the types of complexity that we could handle with refractions and all that kind of good stuff. Images that we couldn’t actually render to full convergence, now were renderable because we could run the denoiser. That allowed us to render images with fewer samples, which was faster, but also let us render more complexity. That cut our render times down quite substantially. “There,” says Sisson, “instead of sending maybe 2,000 samples or 4,000 average samples per pixel, we were able to render with something like 512 average samples per pixel, a big savings at the time. Pixar, of course, comes under the same technology umbrella as Walt Disney Animation Studios, and was able to use this previous denoiser first on Finding Dory (2016). The last couple iterations to achieve full convergence can take as long as the rest of the render simply because the amount of samples required for each iteration grows exponentially.”įor that original denoising tech, Pixar utilized a denoiser that Walt Disney Animation Studios had developed for its Hyperion path tracer on Big Hero 6. “Every time you iterate on the image or the render iterates, it starts to converge. “Path tracers are inherently noisy,” notes Pixar marketing manager Dylan Sisson. Notice here the edges of the leaf are semi-transparent and incorrect.Pixar originally adopted denoising technology once it had rolled out its original RIS path tracer several years ago. However, you may notice that poorly tessellated objects have fringing or incorrect values. Typically this is fine as we default to a dicing scheme that creates micropolygons the size of a pixel or smaller. To avoid some expensive work, we cache the presence value with the micropolygon of the geometry. ![]() You may only need to set the Stochastic Opacity Depth to where the noise is agreeable relative to the rest of the scene instead of literally counting the overlapping surfaces and using that value as the setting. Below are examples at depth 1, 2, and 3ĭepth 1, notice the areas of the plane where there is no stacking are now free of noise.ĭepth 2, notice that planes overlapping one another once are now free from noise.Īs a performance consideration, you may notice that overlapping objects with high levels of opacity will create less noise. However, at each increment, it tells the renderer to composite a semi-opaque color instead of sample randomly at that specified depth and no further. Some production integrators support a solution to this with a parameter called "Stochastic Opacity Depth". Notice that lower presence values will show more noise than higher values. Below we have a set of overlapping planes set to a Presence value of 0.15. This can generate noise and require more samples to clear up or converge. This means we randomly sample at varying levels of presence when the value is not a 0 or 1. By default, we use a stochastic method to determine presence. But you may wish to use partial presence values in rendering for something semi-opaque. This is the traditional way to use the parameter. ![]()
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